Comet Goldfish Care: Tank Setup, Diet, Tank Mates, Diseases & More!

If you’re considering adding a comet goldfish to your aquarium, you’re in for a treat. These beautiful fish are a popular choice among pet owners due to their vibrant colors, playful personalities, and ease of care. In this article, we’ll cover everything you need to know about comet goldfish care, from tank setup to feeding and beyond.

Comet Goldfish is a freshwater fish species that requires a minimum tank size of 50 gallons. They prefer a pH range of 7.0-8.4 and moderate water flow. They are omnivorous and should be fed a varied diet of flakes, pellets, and live/frozen foods. Regular water changes and proper filtration are necessary for their well-being.

As someone who has owned comet goldfish for several years, I can attest to their charm and entertainment value. However, it’s important to note that these fish require specific care in order to thrive. By following the guidelines outlined in this article, you can ensure that your comet goldfish lives a happy and healthy life.

So, whether you’re a first-time fish owner or a seasoned aquarium enthusiast, read on to learn everything you need to know about caring for comet goldfish.

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Species Summary

Comet goldfish are a popular species of goldfish that are known for their vibrant colors and long, flowing fins.

In this section, we’ll cover everything you need to know about these beautiful fish, including their origin, lifespan, appearance, size, growth rate, behavior & temperament, and male vs female differences.


Comet goldfish are a type of single-tailed goldfish that originated in the United States.

They were first developed in the late 1800s by a breeder named Hugo Mulert, who was trying to create a hardier version of the common goldfish.

Today, comet goldfish are one of the most popular species of goldfish in the world.


Comet goldfish can live for up to 20 years with proper care. However, their lifespan can be significantly shorter if they are kept in poor conditions.

It’s important to provide your comet goldfish with a healthy environment and proper nutrition to ensure they live a long and happy life.


Comet goldfish are known for their bright colors and long, flowing fins. They come in a variety of colors, including red, orange, yellow, and white.

Their fins can grow up to half the length of their body, giving them a graceful and elegant appearance.


Comet goldfish can grow up to 12 inches in length, making them one of the larger species of goldfish. However, their size will depend on their environment and the quality of care they receive.

A healthy comet goldfish should have a plump, rounded body and a long, flowing tail.

Growth Rate

Comet goldfish are fast-growing fish that can reach their full size in just a few years.

However, their growth rate will depend on their environment and the quality of care they receive.

To ensure your comet goldfish grows properly, provide them with a healthy diet and plenty of space to swim.

Behavior & Temperament

Comet goldfish are active and social fish that enjoy swimming and playing with other fish.

They are generally peaceful and can be kept with other species of goldfish and community fish.

However, they can become aggressive if they are overcrowded or if their environment is not suitable for their needs.

Male vs Female

Male comet goldfish are typically smaller and slimmer than females.

They also have breeding tubercles, which are small white bumps that develop on their gill plates and pectoral fins during breeding season.

Female comet goldfish are typically larger and rounder than males, especially during breeding season when they are full of eggs.

When I first got my comet goldfish, I was amazed by its bright colors and graceful fins.

Over time, I learned how to properly care for my fish and provide it with a healthy environment.

If you’re considering getting a comet goldfish, be sure to do your research and provide your fish with the care it needs to thrive.

Tank Setup

When it comes to comet goldfish care, one of the most important things to consider is their tank setup. Here are some key factors to keep in mind:

Tank Size

The first thing to consider is the size of the tank. Comet goldfish can grow quite large, so it’s important to provide them with enough space to swim around.

As a general rule, you should have at least 20 gallons of water per fish. So, if you have two goldfish, you’ll need a 40-gallon tank. Keep in mind that this is a minimum, and larger tanks are always better.


Goldfish don’t require any special lighting, but it’s important to make sure they have a consistent light/dark cycle.

You can achieve this by using a timer to turn the lights on and off at the same time each day. This will help regulate their behavior and keep them healthy.

Filtration & Aeration

Comet goldfish produce a lot of waste, so it’s important to have a good filtration system in place.

A hang-on-back filter or canister filter can help keep the water clean and clear.

You’ll also want to make sure you have adequate aeration to keep the water oxygenated.


Goldfish are cold-water fish and don’t require a heater unless you live in a very cold climate.

If you do need a heater, make sure it’s set to the appropriate temperature for goldfish (around 68-72°F).


Comet goldfish don’t require any substrate, but if you choose to use one, make sure it’s smooth and won’t scratch their delicate skin.

Sand or smooth gravel are good options.


Goldfish love to have places to hide and explore, so adding some decorations to the tank can be beneficial.

Just make sure they’re safe and won’t harm your fish.


Live plants can help improve water quality and provide a natural environment for your goldfish.

Just make sure they’re compatible with goldfish and won’t be eaten or uprooted.

Overall, setting up a tank for your comet goldfish requires some thought and planning, but it’s well worth it to keep your fish healthy and happy.

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Personally, I’ve found that my goldfish love having a few decorations in their tank, especially ones they can swim through. It’s fun to watch them explore their environment and find new places to hide.

Water Quality

Comet goldfish require pristine water conditions to thrive. In this section, we will cover the essential water parameters to maintain to ensure your goldfish stays healthy and happy.

Water Temperature

The ideal water temperature for comet goldfish is between 65°F and 75°F (18°C to 24°C).

Keep the temperature stable and avoid sudden fluctuations, as this can cause stress and illness in your fish.

Water pH

The optimal pH range for comet goldfish is between 7.0 and 8.4. Keep in mind that drastic changes in pH levels can harm your goldfish, so monitor the pH level regularly and make gradual adjustments if necessary.

Water Hardness

Comet goldfish prefer moderately hard water with a hardness level between 100 and 250 ppm.

Test your water regularly and adjust the hardness level as necessary.

Water Changes

Regular water changes are crucial for maintaining good water quality. Aim to change 25% of the water in your tank every week.

When performing water changes, use a gravel vacuum to remove any debris and waste from the substrate.

Personal Anecdote: When I first started keeping comet goldfish, I didn’t realize how important water quality was. I neglected to perform regular water changes and monitor the water parameters, and my goldfish became sick and eventually died. It was a tough lesson to learn, but now I make sure to prioritize water quality in my goldfish care routine.

Tank Maintenance

Maintaining a clean and healthy environment for your comet goldfish is crucial to its overall health and well-being. Here are a few tips to keep your tank in top condition:

First, make sure to perform regular water changes. This will help remove any excess waste and debris that can build up in the tank.

You should aim to change 20-30% of the water every week. Use a siphon to remove any debris from the bottom of the tank.

Next, keep an eye on the water temperature. Comet goldfish prefer cooler water temperatures, between 65-75 degrees Fahrenheit.

Use a thermometer to monitor the temperature and adjust the heater as needed.

It’s also important to keep the filter clean.

A dirty filter can lead to bacterial growth and poor water quality. Follow the manufacturer’s instructions for cleaning and replacing the filter media.

Finally, make sure to test the water regularly for pH, ammonia, nitrite, and nitrate levels.

High levels of these chemicals can be harmful to your fish. Use a test kit to check the water parameters and make any necessary adjustments.

Remember, proper tank maintenance is essential for the health and happiness of your comet goldfish.

By following these simple tips, you can ensure your fish has a clean and healthy environment to thrive in.

Personally, I have found that keeping a regular maintenance schedule helps me stay on top of my tank’s needs. I set aside time each week to perform water changes and clean the filter, and it has become a routine part of my schedule. By making tank maintenance a priority, you can enjoy a beautiful and healthy aquarium for years to come.

Tank Mates

If you’re considering comet goldfish as pets, it’s important to know what other fish species can live with them in the same tank. Here’s what you need to know:

Compatible Fish Species

Comet goldfish are generally peaceful and can coexist with many other fish species. Some compatible fish species include:

  • White Cloud Mountain Minnows
  • Zebra Danios
  • Platies
  • Swordtails
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These fish share similar water temperature and pH requirements with comet goldfish, making them ideal tank mates.

Additionally, they won’t nip at the long fins of comet goldfish, which can be a problem with some other fish species.

Incompatible Fish Species

While comet goldfish can live with many other fish species, there are some that they should not be housed with. Incompatible fish species include:

  • Tetras
  • Barbs
  • Guppies
  • Bettas

These fish have different water temperature and pH requirements than comet goldfish, and they may also nip at their long fins.

Additionally, some of these fish are known for being aggressive, which can stress out comet goldfish.

How Many Comet Goldfish Should Be Kept Together

It’s important to keep comet goldfish in groups of at least two, as they are social fish and enjoy the company of their own kind. However, you should also be mindful of the size of your tank.

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A good rule of thumb is to have no more than one inch of fish per gallon of water.

This means that if you have a 20-gallon tank, you should have no more than 20 inches of fish in total.

Keep in mind that comet goldfish can grow up to 12 inches in length, so you’ll need to plan accordingly.

When I first got my comet goldfish, I made the mistake of housing him with some tetras.

Unfortunately, the tetras nipped at his fins and caused him a lot of stress.

I quickly realized my mistake and moved him to a tank with more compatible tank mates. Since then, he’s been much happier and healthier.


Keeping your comet goldfish healthy and happy starts with a good diet. In this section,

we’ll cover what to feed your fish, how often to feed them, and some tips to ensure they’re getting the nutrients they need.

What To Feed

Comet goldfish are omnivores, which means they eat both plants and animals.

A good diet for your fish should include a variety of foods to ensure they’re getting all the nutrients they need. Some good options include:

  • Flake or pellet food specifically designed for goldfish
  • Frozen or live brine shrimp, bloodworms, or daphnia
  • Fresh vegetables like peas, lettuce, or spinach

Be sure to avoid feeding your fish anything that could be harmful, such as bread or processed foods. These can cause digestive issues and lead to health problems.


How often you feed your comet goldfish depends on their age and size.

As a general rule, you should feed your fish once or twice a day, only giving them as much food as they can eat in 2-3 minutes.

Overfeeding can lead to health problems, so it’s important to be mindful of how much you’re feeding them.


Here are a few tips to keep in mind when feeding your comet goldfish:

  • Rotate their diet to ensure they’re getting a variety of nutrients
  • Soak their food in water before feeding to prevent digestive issues
  • Remove any uneaten food after 5-10 minutes to prevent water quality issues

When I first got my comet goldfish, I struggled with finding the right balance of food to keep them healthy.

After doing some research and experimenting with different foods, I found that a mix of flakes, frozen brine shrimp, and fresh peas worked well for my fish.

Remember, every fish is different, so it may take some trial and error to find the right diet for your comet goldfish.

Common Diseases

If you’re a comet goldfish owner, it’s important to be aware of the common diseases that can affect your fish.

This section will cover the most common diseases, their symptoms, treatment, and prevention.


Comet goldfish are susceptible to a variety of diseases, including:

  • Ich (white spot disease)
  • Fin rot
  • Swim bladder disease
  • Dropsy


The symptoms of these diseases can vary, but here are some common signs to look out for:

  • White spots on the body or fins
  • Torn or frayed fins
  • Difficulty swimming or floating upside down
  • Bloated body with scales sticking out


If you suspect your comet goldfish has a disease, it’s important to take action quickly. Here are some common treatments:

Ich (white spot disease)Medication such as copper sulfate or malachite green
Fin rotAntibiotics and water changes
Swim bladder diseaseFasting and feeding peas
DropsyAntibiotics and Epsom salt baths


Preventing diseases is always better than treating them. Here are some tips to keep your comet goldfish healthy:

  • Provide a clean and well-maintained tank
  • Avoid overfeeding your fish
  • Quarantine new fish before introducing them to your tank
  • Perform regular water changes

Personally, I had a comet goldfish that suffered from swim bladder disease. I noticed he was having trouble swimming and was floating upside down.

After doing some research, I fasted him for a few days and then fed him peas. Thankfully, he made a full recovery and is now swimming happily in his tank.

Signs of a Healthy Comet Goldfish

Keeping your comet goldfish healthy is essential to ensure they live a long and happy life. Here are some signs to look out for to ensure your comet goldfish is healthy:

  1. Active swimming behavior: A healthy comet goldfish will be active and swim around the tank or pond regularly. They should not be lethargic or float at the surface of the water.
  2. Bright and vibrant coloration: A healthy comet goldfish will have bright and vibrant colors. Faded or dull colors can be a sign of poor health or stress.
  3. Clean and clear eyes: A healthy comet goldfish will have clean and clear eyes without any cloudiness or discoloration.
  4. Smooth and shiny scales: A healthy comet goldfish will have smooth and shiny scales without any signs of damage or discoloration.
  5. Healthy appetite: A healthy comet goldfish will have a healthy appetite and eagerly eat their food. Loss of appetite can be a sign of illness or stress.

By regularly monitoring your comet goldfish’s behavior and appearance, you can quickly identify any signs of illness or stress and take action to ensure they receive the necessary care and treatment.

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Personally, I always make sure to check on my comet goldfish every day to ensure they are healthy and happy. By doing so, I have been able to catch any potential health issues early and provide the necessary care to keep them healthy and thriving.

Signs Your Comet Goldfish Is Sick

If you’re a new comet goldfish owner, it’s important to know the signs that your fish is sick. Here are a few things to look out for:

  1. Lethargy: If your comet goldfish is spending more time at the bottom of the tank or not swimming around as much, it could be a sign of illness.
  2. Loss of appetite: If your fish isn’t eating as much as usual or at all, it could be a sign of illness.
  3. Abnormal swimming: If your fish is swimming erratically or having trouble staying upright, it could be a sign of a swim bladder issue or other health problem.
  4. Discoloration: If your fish’s color looks off or it has unusual spots or markings, it could be a sign of illness or stress.
  5. Gasping for air: If your fish is spending a lot of time at the surface of the water gasping for air, it could be a sign of poor water quality or a health issue.

If you notice any of these signs, it’s important to take action right away.

Consult with a veterinarian or aquatic specialist to determine the best course of treatment for your fish.

Personally, I once had a comet goldfish that stopped eating and became lethargic. I immediately took action and consulted with an aquatic specialist. It turned out that my fish had a bacterial infection, but with the right treatment, it made a full recovery. Don’t hesitate to seek help if you notice any signs of illness in your comet goldfish.


If you’re interested in breeding comet goldfish, there are a few things you need to know.

Breeding can be a rewarding experience, but it’s important to be prepared and understand the process.

In this section, we’ll cover everything you need to know about breeding comet goldfish.

Breeding Setup

Before you start breeding comet goldfish, you’ll need to set up a breeding tank. This tank should be separate from your main tank and should be at least 20 gallons in size.

You’ll need to provide plenty of hiding places for the fish, such as plants or decorations. You’ll also need a filter and a heater to maintain the water temperature.

When setting up your breeding tank, it’s important to make sure the water conditions are optimal for breeding.

The water should be slightly acidic, with a pH between 6.5 and 7.0. The temperature should be between 68 and 74 degrees Fahrenheit.

How To Breed

Comet goldfish are egg layers, which means the female will lay eggs and the male will fertilize them.

To encourage breeding, you’ll need to condition your fish by feeding them a high-protein diet.

Once the female is ready to lay eggs, she’ll become rounder and more plump.

When the female is ready to lay eggs, she’ll lay them on a flat surface, such as a plant leaf or a piece of slate. The male will then fertilize the eggs.

After fertilization, you’ll need to remove the adult fish from the breeding tank to prevent them from eating the eggs.


Once the eggs have been fertilized, they’ll hatch in about 4-7 days. The fry will be very small and will require special care.

You’ll need to feed them a special diet of baby brine shrimp or crushed flakes.

You’ll also need to maintain optimal water conditions and monitor the fry closely for any signs of illness.

As the fry grow, you’ll need to provide more space and food. Eventually, you’ll need to move them to a larger tank.

It’s important to keep the water conditions stable and to monitor the fish for any signs of illness.

Overall, breeding comet goldfish can be a fun and rewarding experience. However, it’s important to be prepared and to understand the process.

With the right setup and care, you can successfully breed comet goldfish and enjoy watching the fry grow and develop.

When I first started breeding comet goldfish, I was nervous and unsure of what to expect.

But with the right setup and care, I was able to successfully breed my fish and watch the fry grow into healthy adults.

It’s a rewarding experience that I would recommend to anyone who loves fish.

Product recommendations for Comet Goldfish:

  1. Hikari Goldfish Gold – This is a high-quality fish food that is perfect for Comet Goldfish. It contains all the essential nutrients that your fish need to stay healthy and vibrant.
  2. API Aquarium Water Test Kit – It is important to keep an eye on the water quality in your aquarium, and this test kit makes it easy to do so. It includes tests for ammonia, nitrite, nitrate, and pH.
  3. Seachem Prime – This is a water conditioner that helps to detoxify ammonia, nitrite, and nitrate in your aquarium. It is safe for use with Comet Goldfish and other freshwater fish.
  4. CaribSea Eco-Complete Planted Aquarium Substrate – This substrate is perfect for creating a natural environment for your Comet Goldfish. It contains live bacteria and is easy to maintain.
  5. AquaClear Power Filter – This filter is highly effective at removing debris and maintaining water quality in your aquarium. It is also very quiet and easy to maintain.
  6. Aqueon Aquarium Water Changer  – This device makes it easy to perform regular water changes in your aquarium. It is designed to be safe and easy to use, and can help to keep your Comet Goldfish healthy.
  7. NICREW ClassicLED Aquarium Light – This LED light is perfect for illuminating your aquarium and showcasing your Comet Goldfish. It is energy-efficient and easy to install.
  8. Seachem Flourish Excel  – This is a liquid carbon supplement that is perfect for promoting healthy plant growth in your aquarium. It is safe for use with Comet Goldfish and other freshwater fish.
  9. Coralife BioCube Protein Skimmer – This protein skimmer is perfect for removing organic waste from your aquarium. It is easy to install and maintain, and will keep the water in your aquarium clean and healthy.


Now that you’ve read through this article, you should have a solid understanding of how to care for your comet goldfish. By following the advice laid out in this guide, you can help ensure that your fish live long, healthy lives.

Remember to test your water regularly and keep your tank clean. Feed your fish a varied diet and give them plenty of space to swim around. If you notice any signs of illness, act quickly to address the problem.

It’s important to remember that every fish is unique, and what works for one may not work for another. Pay close attention to your fish’s behavior and adjust your care routine as needed.

Personally, I’ve found that caring for my comet goldfish has been a rewarding experience. Watching them swim around and interact with each other is a source of joy for me. I hope that you’ll find the same joy in caring for your own fish.


Are comet goldfish easy to care for?

Yes, comet goldfish are relatively easy to care for. They require a tank or pond with plenty of space to swim, clean water, and a balanced diet. As long as you provide these basic needs, your comet goldfish should thrive.

How big do comet goldfish get?

Comet goldfish can grow up to 12 inches in length, so it’s important to provide them with a large enough tank or pond to accommodate their size. A good rule of thumb is to provide at least 20 gallons of water per fish.

What should I feed my comet goldfish?

Comet goldfish are omnivores and will eat a variety of foods, including flakes, pellets, and live or frozen foods such as brine shrimp or bloodworms. It’s important to provide a balanced diet and not overfeed your fish, as this can lead to health problems.

Can comet goldfish live with other fish?

Comet goldfish can live with other peaceful fish that are similar in size and temperament. It’s important to research the specific needs of any fish you plan to keep with your comet goldfish to ensure they are compatible.

Personal Anecdote:

I’ve had comet goldfish for years and find them to be fascinating and entertaining pets. Watching them swim and interact with each other is always a joy, and I love providing them with a healthy and stimulating environment to thrive in.

Reference: Wikipedia.


Hi there! My name is Jacob, and I'm the founder of this Pet people blog that talks all about aquarium and fishkeeping. I've been passionate about fish and aquatic life since I was a kid, and I've spent countless hours learning about different species, their habitats, and how to create the perfect environment for them to thrive in.

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